The present invention relates generally to coaxial connectors, whether male or female and, more particularly, to a connector including an insulating structure having plural radii between coaxial inner and outer conductors, wherein (1) the insulating structure receives the inner conductor in an opening having a smaller diameter than a standard inner conductor diameter and (2) the connector has a predetermined characteristic impedance             Z      0        =                  60                              ε            r                              ⁢              ln        ⁡                  [                      D            d                    ]                      ,
where xcex5r is the dielectric constant of an insulator between the conductors, d is the outer diameter of the standard inner conductor and D is the inside diameter of the outer conductor.
In accordance with German DIN standard 47 223, a {fraction (7/16)} coaxial connector has an outside diameter (d) of an inner conductor of about 7 mm and an inside diameter D of an outer conductor of about 16 mm. With air as the dielectric between the inner and outer conductors, such a connector, whether male or female, has a constant characteristic impedance of 50 xcexa9. The family of {fraction (7/16)} coaxial connectors, whether male or female, is appropriate to connect tubular coaxial conductors and flexible cables preferably having an outer conductor with an effective inside diameter between 10 mm and 20 mm. Such connectors usually include an insulating disk to support and brace the inner conductor within the outer conductor. The insulating disk supports a bush-shaped inner conductor of a female coaxial connector and a pin-like inner conductor of a male coaxial connector. The insulating disk is made of an insulator material having a dielectric constant xcex5r enabling the connector to have a characteristic impedance       Z    0    =            60                        ε          r                      ⁢          ln      ⁡              [                  D          d                ]            
to satisfy the wave equation.
Because the dimensions of d=7 mm and D=16 mm are selected for air as the dielectric between the inner and outer conductors, the inner conductor must have a smaller diameter in the vicinity of the disk in order for the wave equation to provide the desired 50 xcexa9 characteristic impedance. For that reason the inner conductor of a {fraction (7/16)} coaxial connector per DIN 47 223 is constricted in the vicinity of the insulating disk. On both sides of the insulating disk, that is on both sides of the constriction, the inner conductor has a standard 7 mm outside diameter. The constriction of the inner conductor diameter is a substantial drawback to use of {fraction (7/16)} coaxial connectors having insulating disks, because of the complexity encountered in manufacturing and assembling such coaxial connectors. It is impossible simply to push the inner conductor through the insulating disk.
Accordingly, an object of the present invention is to provide a new and improved coaxial connector having a solid dielectric separating the connector inner and outer conductors, wherein the dielectric is made to simplify manufacture and assembly of a functionally reliable connector without changing the connector characteristic impedance.
A coaxial connector in accordance with the invention comprises an outer conductor (having an inner diameter D), an inner conductor (having an outer diameter d) coaxial with the outer conductor, and an insulating structure between the conductors. The diameters are selected in such a manner that, according to the wave equation, a predetermined characteristic impedance       Z    0    =            60                        ε          r                      ⁢          ln      ⁡              [                  D          d                ]            
is attained. The connector has a first cable side adapted to be connected to a coaxial cable and a second connection side adapted to be connected to a corresponding coaxial connector. The insulating structure has a dielectric constant xcex5 and is mounted in proximity to the second end and remote from the first end. The insulating structure has a substantial length along the longitudinal axis of the inner conductor and includes a first portion that is fixedly mounted relative to the outer conductor. The insulating structure includes an opening through which the inner conductor passes. The opening has a smaller diameter than d, as does the outer diameter of the portion of the inner conductor which passes through the opening.
The insulating structure has differing radii between the inner and outer conductors along its length. The insulating structure radii, the opening diameter and the insulating structure dielectric constant xcex5r are such that the predetermined characteristic impedance Zo of the wave equation is attained where the insulating structure is located to compensate for the dielectric properties of the insulating structure.
Preferably, the insulating structure includes a first disk like portion and a second portion extending from the disk like portion toward the second end. The first portion has a constant diameter equal to D, while the second portion has a constant diameter between d and D. Preferably, the diameter of the second portion is less than D/2.
The insulating structure is preferably constructed in such a manner that the reduced diameter inner conductor does not include a constriction at the connection-side of the insulator structure. As a result, the coaxial connector can be assembled in a simple manner by merely pushing the inner conductor through the insulator. The values of d and D of the coaxial connector make it possible to connect the connector, without need for compensation, in the region of an electrical or mechanical reference plane to a standard d/D coaxial connector. Moreover, despite the reduced outer diameter of the inner conductor at the connection-side end of the insulating disk, relative to the standard inner conductor diameter, d, the inside diameter D of the outer conductor is unchanged at the connection-side end of the coaxial connector. As a result no jump occurs when a coaxial connector of the present invention is connected to a cable having the standard values of d and D or to another connector having an insulating structure in accordance with the invention. Such a connection between the outer conductor of the connectors defines both a mechanical and an electrical reference plane. Because no jump occurs no compensation is necessary to attain the predetermined characteristic impedance Z0.
In one embodiment, the coaxial connector is a male coaxial connector with an inner conductor in the form of a pin. The insulating structure is fixed in place at the connection-side end of the connector in a stable and very easily implemented manner in such a male coaxial connector. The connector outer conductor includes a metal ring abutting the insulating structure. The metal ring outer diameter is the same as the outer conductor inner diameter. The metal ring is preferably a press-fitted metal ring, extending between the insulating structure and an electrical and mechanical reference plane formed by an interface between the outer-conductors of the male connector and a mating female connector. The female connector preferably has an insulating structure similar to the male connector or a convention female connector of an end of a coaxial cable. In another embodiment, the coaxial connector is a female connector having a bush-shaped inner conductor having a connection interface region with a mating male connector. The interface region of the bush-shaped inner conductor includes slits circumferentially distributed over the interface. The slits form an elastic chuck. This design offers the particular advantage that the slitted portion of the inner conductor bears against a wall defining the inner diameter of a second portion of the insulating structure having an outer diameter less than D, and preferably less than D/2.
The insulating structure wall braces the chuck segments. If the female connector is connected to a male connector in such a way that the male and female connectors are not exactly aligned, bending or breaking of the chuck segments does not occur, even though the chuck segments have a thinner wall relative to a standard female connector because of support for the chuck segments the wall provides.
Appropriately, the coaxial connector is a {fraction (7/16)} coaxial connector, illustratively a {fraction (7/16)} coaxial female connector or a {fraction (7/16)} coaxial male connector having a characteristic impedance Z0=50 xcexa9. Many high-frequency applications are covered, for instance mobile-radio base stations, where the desired characteristic impedance Z0=50 xcexa9.
The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed descriptions of plural specific embodiments thereof, especially when taken in conjunction with the accompanying drawings.